/*
 *  Copyright (c) 2011-2015 The original author or authors
 *  ------------------------------------------------------
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  and Apache License v2.0 which accompanies this distribution.
 *
 *       The Eclipse Public License is available at
 *       http://www.eclipse.org/legal/epl-v10.html
 *
 *       The Apache License v2.0 is available at
 *       http://www.opensource.org/licenses/apache2.0.php
 *
 *  You may elect to redistribute this code under either of these licenses.
 */
package com.taobao.middleware.cli.converters;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * This 'default' converter tries to create objects using a static 'valueOf' method taking a single String argument.
 * This converter is particularly convenient to for enumeration and primitive types.
 *
 * @author Clement Escoffier <clement@apache.org>
 */
public final class ValueOfBasedConverter<T> implements Converter<T> {

    public static final String VALUE_OF = "valueOf";
    private final Method method;
    private final Class<T> clazz;

    private ValueOfBasedConverter(Class<T> clazz, Method method) {
        this.clazz = clazz;
        this.method = method;
    }

    /**
     * Checks whether the given class can be used by the {@link ValueOfBasedConverter} (i.e. has a static 'valueOf'
     * method taking a single String as argument). If so, creates a new instance of converter for this type.
     *
     * @param clazz the class
     * @return a {@link ValueOfBasedConverter} if the given class is eligible,
     * {@literal null} otherwise.
     */
    @SuppressWarnings("unchecked")
    public static <T> ValueOfBasedConverter<T> getIfEligible(Class<T> clazz) {
        try {
            final Method method = clazz.getMethod(VALUE_OF, String.class);
            if (Modifier.isStatic(method.getModifiers())) {
                if (!method.isAccessible()) {
                    method.setAccessible(true);
                }
                return new ValueOfBasedConverter(clazz, method);
            } else {
                // The valueOf method is present but it must be static.
                return null;
            }
        } catch (NoSuchMethodException e) {
            // The class does not have the right method, return null.
            return null;
        }

    }

    /**
     * Converts the given input to an object by using the 'valueOf' method. Notice that the method may
     * receive a {@literal null} value.
     *
     * @param input the input, can be {@literal null}
     * @return the instance of T
     * @throws IllegalArgumentException if the instance of T cannot be created from the input.
     */
    @Override
    public T fromString(String input) throws IllegalArgumentException {
        try {
            return clazz.cast(method.invoke(null, input));
        } catch (Throwable e) {
            if (e.getCause() != null) {
                throw new IllegalArgumentException(e.getCause());
            } else {
                throw new IllegalArgumentException(e);
            }
        }
    }
}
